So, just in case I wasn't the last one to find out. GHash is no longer mining dash as of the 15th. For some reason they're still accepting hashes & the DRK page is still there when you log in, but hashes are going to nothing as of the 15th. FYI
Reference...
That'll happen occasionally. nothing to worry about. I've been mining for almost a year with 2 GTX 970's in 2 PC's. Once every few minutes (on both/either comptuers) I'll get an error that one of the hashes from one of the GPU's didn't validate on the CPU, but I still get plenty of shares from...